Heat treated copper-nickel-molybdenum steel article and process of making the same



, ma s 18, 1943 UNITED STATES fPATENT OFFICE HEAT TREATEDCOPPERHNICKEL-MOLYB- DENUM STEEL ARTICLE AND rnocnss OF MAKING THE SAMEJohn Mitchell, Chicago, Ill.

No Drawing. Application July 17, 1941, Serial No. 402,850 7 '7 Claims.

ties together with higher ultimate strength .without loss of ductility.

Further objects and advantages of the present invention will becomeapparent as the description proceeds-and the features of novelty will bepointed out in detail in the appended claims.

loys. It is adapted particularlyto applications where the maximumcorrosion resistance is, required when the parts are subject to tensilestresses, compressive stresses, torsional stresses,

bending stresses, and/or alternations of each, in

the presence of corrosive media; existing'individually as salt or salinewaters, sulphuric or hydrochloric acids or existing as combinations ofsuch mineral acids and/or in the presence of hydrogen sulphide gas,and/or crude petroleum oils, and the present alloy possesses highlyimproved corrosion fatigue, together with the requisite high strengthand ductility.

The alloy of the present invention contains carbon from about 0.03% toabout 0.40%; manganese 0.21% to about 4.00%; phosphorus from the usualamounts present in all steels, i. e., from In its specific aspects, thepresent invention pertains to a copper-mckel-molybdenum steel; and whilesucker rods may be regarded as a specific adaptation of the invention,it will be apparent that it is adapted for many uses which require highstrength combined with high ductility and res stance to corrosion understress.

Taking sucker rods as a specific example, it

y e note that ordinarily corrosion-fatigue-.

resisting sucker rods are made from steels of approximately 0.20%carbon, 0.70%, manganese, .7 nickel, 0.20%-0.30% molybdenum, the al- 10ybeing normalized to produce 85,000-90,000 psi ultimate strength withhigh ductility or normalized and drawn to produce approximately80,000-85,000 psi ultimate strength with high ductility. These suckerrods are produced also from steels called low metalloid steels or ironscontaining low carbon (approximately 0.07%),-

manganese 0.20% maximum, ickel I 3.50%. molybdenum 0.25%, quenched antempered to approximately 65,000 psi with accompanying high ductility.Both of these steels function well in corrosive media under stress, theformer permitting the smallest possible rod size due to its strengthwith fair corrosion resistant results.

The latter alloy is superior in corrosion resist-- ance, but is .notalways feasible or economical to use in pumping of deep wells due to thelow strength which necessitates increased rod size. 4 i The steel of thepresent invention constitutes a definite improvement over the foregoingalabout 0.005% to about 0.20%; silicon up to about 0.50%; nickel fromabout 0.50% to about 5.00%; copper from about 0.50% to about 2.00%;

and molybdenum up to 0.5%, the balance being v substantially all iron.

'A typical analysis and physical properties of the present improvedsteel are as follows:

Carbon 0.08%; manganese 0.32%; silicon 0.24%; phosphorus p nickel 3.22%copper 1.15%; molybdenum 0.28%, balance substantially iron.

This compositon has the following as-rolled properties:

Yield point, psi 70,000 Ultimate strength, psi 93,000 Elongation in 2inches per cent-.. 38 Elongation in 4 inches do.... 25 Elongation in 8inches do 19 Reduction of area do.. 65 Charpy impacts "ft. lbs 55 Izodimp cfs 100 The tensile tests were pulled in full section round.

The desired physical properties of the improved alloy are obtained byheating the steel to a temperature in excess of the Ac: point, followedby cooling in air to approximately 700 F. or less, followed by reheatingto approximately 825 F. to 1200? F., followed by cooling in air. Thisreheating operation to'825" F. to 1200 F. ordinarily reduces thestrength of the steel so treated whereas in the improved alloy of thisinvention the steel or iron actually increases in strength with noappreciable decrease in ductility. Where steels or irons increase instrength in this operation, theterm accelerated age hardening orprecipitation hardening applies, either of which is referred tohereinafter as normalizing and drawing, or where the hot-rolled bar isdrawn.

Typical properties of-the improved composition as normalized from 1650F. are as follows:

Yield point, psi 62,000 Ultimate strength, psi 86,900 Elongation in 2inches per cent 40 Elongation in 4 inches do 28 Elongation in 8 inchesdo 21 Reduction of area do 65 Charpy impacts ft. lbs 56 Izod impacts 'do111 Typical physical properties when normalized at 1650 F. and drawn at1000" F., or asrolled,

air-cooled and drawn .at 1000 F. are as follows:

Yield point, psi 70,000 Ultimate strength, psi- 94,000 Elongation in 2inches per cent 33 Elongation in 4 inches do 21 Elongation in 8 inchesdo 15 Reduction of area do 62 Charpy impacts ft. lbs 54 Izod impacts do104 All the above tensile properties were determined on the full sectionof A" round bar. The Izod tests were machined to standard dimensionsafter treatment.

In the foregoing, the term normalized refers to heating above the A03point and cooling in air; the term normalized and drawing referring toheating above the A03 point, cooling in air followedby reheating to anytemperature below the A01 point, followed by cooling in air; the termquenching and tempering as used herein referring to heating to atemperature in excess of the AC3 point, followed by sud-dent cooling ina liquid medium, followed by reheating to any temperature below the A01point, followed by cooling in air.

In accordance with the present invention, the desired physicalproperties are obtained by heating the improved alloy to a temperaturein excess of the A03 point, followed by cooling in air to approximately700 F. or less-followed by reheating to approximately 825 F. toapproximately 1200" F., followed by cooling in air. While in the case ofthe steels of this type of the prior art, this reheating to 825 F.-1200F. ordinarily reduces the strength of the steel so treated, in the caseof the steels of the present invention the reheating actually increasestheir strength with no appreciable decrease in ductility.

The proper balance of the alloying elements of the present inventionwhen normalized and drawn, produces in sizes up to about one inch crosssection an ultimate strength of about 95,000 psi. This is 30,000 psi inexcess of the values obtainable with low metalloid irons and also is inexcess of the normalized steels commonly used for the purposes for whichthe present improved alloy is suitable. As to corrosion fatigue, theactual comparison of the present improved alloy in corrosion fatiguetests subjected to an outer fiber stress of 30,000 psi in the presenceof a corrosive medium simulating the composition of natural occurringoil well liquids and hydrogen sulphide gas, with air excluded, has run2,000,000

cycles of stress to failure as compared with 1,000,000 cycles ordinarilyobtained with the said standard alloys.

As has been indicated above herein, the present improved steel isadapted particularly to applications where the maximum corrosionresistance is required. when the parts are subject to tension,compression, torsoin, bending stresses, and/oralternation's of each; inthe presence of corrosive mediaexisting individually as salt or salinewaters, sulphuric or hydrochloric acids, or existing as combinations ofsuch mineral acids and/or in the presence of hydrogen sulphide gas.

The present improved alloy also is adapted to chain steel or similarapplications where the parts come in contact with hot metal, reachingtemperatures up to 1000 F. which reduce the strength of quenched andtempered chain steels of commonly used compositions, but which, ontheother hand, do not afiect the strength of the present improved steel.

It will be seen from the foregoing that the specific heat treatment toobtain the maximum properties of the improved alloy consists innormalizing by heating to any temperature above the A03 point, andcooling in air, this normalizing being followed by reheating to atemperature between about 800 F. to about 1200 F., and cooling in air,or by using the single treatment of drawing, between 800 F. to 1200 F.Without any prior treatment, when hot-rolled material is hot-finishedabove the A3 point.

Thus, for example, in accordance with the present invention there areproduced heat treated steel articles having excellent corrosionresistance as indicated above, such articles being composed of carbonapproximately 0.1%, manganese approximately 0.4%, copper approximately1%, nickel approximately 3.5%, and molybdenum approximately 0.2%, thebalance being iron except for normally present impurities, the articlesbeing characterized by a normalized structure produced by normalizingthe steelfrom a temperature above its Aca point, then reheated tobetween approximately 800 F. to approximately 1200 F. and then cooled inair.

,As illustrative of such articles, there are pro- I temperature between800 F. and 1200 F., cooled drawn structure imparted by being normalizedfrom above the A03 point of the steel, reheated to a temperaturebetween800 F. and 1200 F., cooled again in air and drawn at a temperaturebetween 800 F. and 1200 F.

. approximately 3.5%, and molybdenum approximately 0.2%, the balancebeing iron except for normally present impurities, the said articlebeing characterized by a normalized structure produced by normalizingthe steel from a temperature above its Aca point, then reheated tobetween approximately 800 F. toapproximately 1200 F'., and then cooledin air.

4. A method of producing a steel article which is highly resistant tocorrosion in the presence of salt water, hydrogen sulphide gas, andmineral acids, the said article'being composed of a steel consisting ofnot more than approximately 0.30% carbon, from approximately 0.5% toapproximately 1% of manganese, from approximately 0.5% to approximately1.25% copper,-- from approximately 1.5% to approximately 3.5% nickel,from approximately 0.2% to approximately 0.5% molybdenum, balancesubstantially all iron, which method comprises heating the steel in"asis highly resistant to corrosion in the presence of salt water,hydrogen sulphide gas, and mineral acids, the said article beingcomposed of a steel consisting of not more than approximately 0.30%carbon, from approximately 0.5% to approximately 1% of -manganese, fromapproximately 0.5% to approximately 1.25%.. copper, from approximately1.5% to approximately 3.5% nickel, from approximately 0.2% toapproximatey 0.5% molybdenum, balance substantially all iron, whichmethod comprises hot rolling and hot finishing the steel above its Ac:point. and drawing the steel at between 800 F. to 1200 F.

6. A heat treated steel article composed of not more '-than 0.3% carbon,'from approximately 0.5% to approximately 1% manganese, from aprolled oras-iorged condition to temperatures proximately 1200 F., and drawingwithin this temperature range.

5. A method of producing a steel article which proximately 0.5% toapproximately 1.25% copper, from approximately 1.5% to approximately3.5% nickel and from approximately 0.2% to approximately 0.3%molybdenum, remainder iron except for normal impurities, the articlebeing characterized by having a normalized structure imparted by beingnormalized from above the Ac: point of the steel, reheated to atemperature between 900 F. and 1200 F., and cooled.

7. The method .of producing a heat treated steel article composed of notmore than 0.3% car bon, from approximately 0.5% to approximately 1%manganese, from approximately 0.5% to approximately 1.25% copper, fromapproximately 1.5% to approidmately 3.5% nickel, and from approximately0.2% to approximately 0.3% molybdenum, remainder iron except for normalimpurities, which method consists in heating the steel in excess of theAc: point, cooling to 700 F. r

or lower, reheating .to between approximately 800 F. to approximately1200 F. and then 0001- ing.

JOHN MITCHELL.

